Fuel cell power generation equipment and a device using the same

ABSTRACT

An object of the present invention is to obtain a fuel cell power generation equipment most suitable for a portable power source without requiring any auxiliary equipment such as a separator and a fluid feeder. According to the present invention, a fuel cell power generation equipment is provided, in which an anode for oxidizing fuel and a cathode for reducing oxygen are formed with an electrolyte membrane in between and liquid is used as a fuel, wherein one or more air vent holes are provided on a wall surface of a fuel container  1 , multiple unit cells having an electrolyte membrane, an anode and a cathode are mounted on a wall surface of said fuel container, and the unit cells are electrically connected each other.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a fuel cell power generationequipment comprising an anode, an electrolyte membrane, a cathode and adiffusion layer, wherein fuel is oxidized at an anode and oxygen isreduced at a cathode, in particular, compact type portable power sourceusing liquid fuel such as methanol as a fuel and mobile electronicdevices using this power source.

[0002] Recent progress in electronics technology has contributed tominiaturizations of telephone set, notebook type personal computer,audio visual devices or mobile information terminal devices, and theiruse is increasingly prevailing as portable electronics devices.

[0003] Heretofore, these portable electronics devices were driven by asecondary battery, and have been developed through the appearances ofnew type secondary batteries from sealed lead battery to Ni/Cd,Ni/hydrogen and further Li ion batteries, and modifications to morecompact and light weight types and higher energy density types. In anyof these secondary batteries, cell active materials to enhance an energydensity or cell structure having a higher capacity have been developedand efforts have been paid to obtain a power source with longer servicetime per one charge.

[0004] However, secondary batteries still have many problems for a longcontinuous drive of portable electronics devices because charging isindispensable after consuming a certain amount of power, and a chargingequipment and a relatively longer charge time are required. Now,portable electronics devices are progressing towards devices requiring apower source enabling to supply a higher output density and a higherenergy density, that is, a power source with a longer continuous servicetime, in response to an increasing volume of information and a highercommunication speed in the future. Therefore, a need for a compact powergenerator (a micro power generator) serviceable without charging hasbeen heightened.

[0005] As a power source responding to such requirement, a fuel cellpower source is considered. Since a fuel cell directly convertselectrochemically a chemical energy of fuel to an electric energy anddoes not require a driving unit like in a power generator using aninternal combustion engine such as a usual engine-driven generator, itsrealization as a compact power generator device is highly possible. Afuel cell also does not require to temporary stop an operation ofequipment for charging as in a usual secondary battery, because it cancontinue a power generation so long as a fuel is supplied.

[0006] For these requirements, a solid polymer type of fuel cell (PEFC:Polymer Electrolyte Fuel Cell) is known as a battery with a high outputdensity, which generates power by oxidizing hydrogen gas at an anode andreducing oxygen at a cathode using an electrolyte membrane made of aperfluorocarbon sulfonic acid based resin.

[0007] To further miniaturize this fuel cell, for example, as disclosedin JP-A-9-223507, a compact type of PEFC power generation equipment hasbeen proposed, in which cylindrical batteries equipped with anode andcathode electrodes at inner and outer surfaces of hollow fiber typeelectrolyte are assembled, and hydrogen gas and air are fed to inner andouter parts of the cylinder, respectively. However, in the applicationto a power source for portable electronics devices, a large volume offuel tank should be provided due to a lower volume energy density of afuel because the fuel used is hydrogen gas.

[0008] This system also requires auxiliary equipment such as anequipment to feed a fuel gas or an oxidizing gent gas (such as air) to apower generation equipment or to humidify electrolyte membrane tomaintain the cell performance, which complicates a composition of powergeneration system and thus the system is not sufficient to attainminiaturization.

[0009] In order to raise a volume energy density of fuel, it iseffective to use a liquid fuel and to eliminate auxiliary equipment tofeed a fuel or an oxidizing agent to cell to obtain a simplecomposition. Such example has been proposed in JP-A-2000-268835 andJP-A-2000-268836, disclosing a direct type methanol fuel cell (DMFC:Direct Methanol Fuel Cell) using methanol and water as fuels.

[0010] This power generation equipment has an anode which is arranged ina manner to contact with outer wall side of a liquid fuel container viaa material to feed liquid fuel by a capillary force, and is furthercomposed of a solid polymer electrolyte membrane and a cathode connectedsequentially.

[0011] This type of power generating equipment features in a simplecomposition not to require any auxiliary equipment to feed a fuel and anoxidizing agent thanks to a diffusive feed of oxygen to outer surface ofa cathode which is exposed to ambient air, and also in a requirement foran electrical connection only without any separator as a connecting partfor unit cells when multiple cells are combined in series.

[0012] However, since an output voltage per unit cell of DMFC under loadis 0.3 to 0.4 V, DMFC requires a connection of cells in series by usingmultiple fuel tanks attached to a fuel cell to respond to a voltagerequired by portable electronics. Miniaturization of power generationequipment also requires increased number of cells in series andreduction of a fuel container volume per unit cell, remaining a problemthat fuel container is divided into multiple containers in response to anumber of cells in series.

[0013] In addition, a continuous service becomes difficult unless somedischarging mechanism is realized for a gas generated in a liquid fueltank by an oxidation reaction at an anode with an operation of this acidtype electrolyte fuel cell.

[0014] An object of the present invention is to provide a fuel cellpower generation equipment easily and continuously serviceable byfeeding a fuel, without charging after consumption of a certain amountof power like a secondary battery, and a system using a fuel having ahigh volume energy density.

[0015] Another object of the present invention is to provide a compactpower source most suitable for portable use as well as portableelectronics devices using the same, wherein a fuel cell power generationequipment is composed of unit cells comprising an anode, an electrolytemembrane and a cathode laminated with a separator having a conductivefluid channel structure in between to obtain a specified voltage, thepower source being a compact fuel cell without having an auxiliaryequipment such as a fluid feeding mechanism instead of a conventionalfuel cell having a fluid feeding mechanism which enforces passingthrough of a fuel and an oxidizing agent gas, enabling feeding a liquidfuel to each unit cell in any position of power source, and having adischarging function for a gas oxidized and generated in an anode from afuel container.

SUMMARY OF THE INVENTION

[0016] Summary of the present invention which attains the abovedescribed objects is as follows.

[0017] A fuel cell power generation equipment is provided in which ananode to oxidize fuel and a cathode to reduce oxygen are formed with anelectrolyte membrane in between and a liquid is used as a fuel, whereinthe equipment has one or more air venting hole in a wall surface of afuel container, and multiple unit cells having an electrolyte membrane,an anode and a cathode are mounted on said wall surface of fuelcontainer, and the unit cells are electrically connected each other.

[0018] A liquid fuel container is used as a platform, and multiple unitcells, consisting of an anode, a cathode and an electrolyte membrane,are mounted on its outer wall surface.

[0019] In particular, in the case when a relatively low current and ahigh voltage are required, a high voltage can be obtained by arrangingmultiple unit cells consisting of an anode, an electrolyte membrane anda cathode on an outer circumferential surface of a fuel container andconnecting each unit cell in series or in combination of series andparallel with conductive interconnectors.

[0020] A fuel can be fed without installing auxiliary equipment tocompulsively feed fuel to each unit cell, by connecting a fuel containeras a platform. In this case, feeding of a fuel is further stabilized byretaining liquid fuel in a liquid fuel container and filling a materialto suck up fuel by capillary force.

[0021] On the other hand, an oxidizing agent is fed by a diffusion ofoxygen in air to each unit cell having a power generation part at outerwall surface of the liquid fuel container. A longer power generation canbe continued by using a liquid fuel having a high volume energy densitysuch as aqueous methanol solution as a fuel in comparison with the casewhen hydrogen gas is used as a fuel in the same volume of container.

[0022] By using a power source comprising a fuel cell in accordance withthe present invention as a battery charger which is used to charge upsecondary battery mounted cellular phone, portable personal computer,portable audio, visual equipment and other portable informationterminals, during a temporary stop operation, or by using the powersource directly as a built-in power source without mounting a secondarybattery, it becomes possible to extend service times of theseelectronics devices and use continuously by feeding a fuel.

[0023] Other objects, features and advantages of the invention willbecome apparent from the following description of the embodiments of theinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024]FIG. 1 is a drawing of cross-sectional structure of a fuelcontainer of the present invention.

[0025]FIG. 2 is a schematic drawing showing a composition of anelectrode/electrolyte membrane assembly of the present invention.

[0026]FIG. 3 is a cross-sectional drawing of a fuel cell fixing plate ofthe present invention.

[0027]FIG. 4A and FIG. 4B are drawings of cross-sectional structures ofan air vent hole and a container fitting part of the present invention.

[0028]FIG. 5 is a composition drawing of a mounting part of a fuel cellof Example 1.

[0029]FIG. 6 is an appearance drawing of a fuel cell power generationequipment of Example 1.

[0030]FIG. 7A and FIG. 7B are appearance and cross-sectional drawings ofa separator of Comparative Example 1.

[0031]FIG. 8 is a composition drawing of a laminated composition of afuel cell of Comparative Example 1.

[0032]FIG. 9 is a composition drawing of an outer plate of a highvoltage type rectangular tube shaped unit cell of the present invention.

[0033]FIG. 10A and FIG. 10B are drawings showing an appearance structureof a power source and a connection of power source/fuel tank ofComparative Example 1.

[0034]FIG. 11 is a composition drawing of electrode/electrolyte membraneassembly of Example 1.

[0035]FIG. 12 is an appearance drawing of a fuel cell power generationequipment of Example 1.

[0036]FIG. 13 is a cross-sectional drawing of a fuel cell powergeneration equipment of Example 1.

[0037]FIG. 14 is an appearance drawing of a fuel cell power generationequipment of Comparative Example 2.

[0038]FIG. 15 is a cross-sectional drawing of a fuel container ofExample 2.

[0039]FIG. 16 is a composition drawing of mounting part of a fuel cellof Example 2.

[0040]FIG. 17 is a cross-sectional drawing of a fuel container ofExample 3.

[0041]FIG. 18 is an appearance drawing of a fuel cell power generationequipment of Example 4.

[0042]FIG. 19 is an appearance drawing of a fuel cell power generationequipment of Example 5.

EXPLANATION OF NUMERALS

[0043]1 . . . fuel container, 2 . . . mounting part of fuel cell, 3 . .. diffusion hole, 4 . . . interconnector, 5 . . . suction material forliquid fuel, 6 . . . fuel cell terminal, 7 . . . cathode currentcollector, 8 . . . fixing plate for fuel cell, 9 . . . MEA(electrolyte/electrode assembly), 10 . . . gasket, 11 . . . diffusionlayer, 12 . . . aqueous methanol solution, 13 . . . unit cell, 15 . . .air vent hole, 16 . . . output terminal, 17 . . . fastening band, 18 . .. fuel retaining layer, 19 . . . mounting hole of air vent hole, 20 . .. insulation layer, 21 . . . electrolyte membrane, 22 . . . anode layer,23 . . . cathode layer, 50 . . . steam separation membrane, 51 . . . airvent tube, 52 . . . air vent lid, 54 . . . rib part, 81 . . . separator,82 . . . manifold, 83 . . . longitudinal cross-section of a separator,84 . . . lateral cross-section of a separator, 85 . . . opening part forpower generation, 86 . . . manifold opening part, 87 . . . manifoldinsertion part, 88 . . . channel insertion part, 89 . . . rib part, 92 .. . liner, 93 . . . sucking material, 94 . . . laminated cell, 102 . . .fuel tank, 103 . . . mounting part of fuel cell and 105 . . . cellholder.

DETAILED DESCRIPTION OF THE INVENTION

[0044] Typical embodiments of the present invention are explained indetail with reference to drawings. FIG. 1 is an example ofcross-sectional structure of a liquid fuel container composing thepresent invention.

[0045] Multiple mounting parts 2 for a fuel cell having an insulatingsurface are fitted on an outer wall surface of a fuel container 1, andin a container wall of said mounting part 2 of fuel cell, a net-likestructure, a porous layer or a slit-like diffusion hole structure 3through which a liquid fuel sufficiently permeates is formed in advance.

[0046] An anode side interconnector 4 is formed on a surface of themounting part 2 of fuel cell by coating and baking a corrosion resistantand conductive material to electrically connect to an adjacent fuelcell. The interconnector 4 has a net-like structure, a porous layer or aslit-like diffusion hole structure through which a liquid fuelsufficiently permeates.

[0047] An electrochemically inactive liquid fuel sucking material 5 ismounted on an inner wall surface of a fuel container 1. Fuel cellsmounted on a wall surface of a fuel container are electrically connectedin series or in combination of series and parallel, and fuel cellterminals 6 of an anode and a cathode are equipped to take out powerfrom a power generation equipment.

[0048] In a unit cell, as shown in FIG. 2, an anode layer 22 and acathode layer 23 are assembled in one piece on both surfaces of a solidelectrolyte membrane 21, and an electrolyte membrane/electrode assembly(MEA) is formed in advance. A fixing plate 8 for fuel cell to fix a fuelcell to a fuel container uses an electrically insulating material asshown in FIG. 3, wherein a portion in contact with a fuel cell has anet-like structure, a porous layer or a slit-like diffusion holestructure 3 through which air sufficiently diffuses to be fed to a fuelcell, and a part of surface of the diffusion hole in contact with a fuelcell has a cathode current collector plate 7 to connect to an anode sideinterconnector 4 of an adjacent fuel cell.

[0049] A part of this cathode current collector plate 7 in contact witha fuel cell has a diffusion hole 3 through which air is sufficientlyfed. In a fuel cell 1, carbon dioxide is formed by an oxidation of afuel during power generation, which is discharged to outside of a fuelcontainer through an air vent hole 15 having a gas/liquid separationfunction and being impermeable for liquid with a cross-sectionalstructure as shown in FIG. 4A.

[0050] An air vent hole 15 is composed of an air vent tube 51 and ascrew-fastening type of air vent lid 52, having a structure to fix awater-repellant and porous gas/liquid separation membrane 50 with an airvent lid. The air vent holes 15 are arranged on a plurality of surfacesof a fuel container 1 so that at least one hole is in a ventilatingstate in any position of a fuel cell power generation equipment as thecross-sectional structure shown in FIG. 4B.

[0051] As shown in FIG. 5, a fuel cell power generation equipment isassembled by laminating gasket 10, MEA 9, gasket 10 and a porousdiffusion layer 11, which is a woven fabric of carbon fiber finelydispersed with polytetrafluoroethylene to make diffusions of air andwater formed easy, on a fuel cell mounting part of a fuel container inthis order, and fixing a fuel cell fixing plate having mounting holes 19for air vent holes to a fuel container 1 by an adhesion or ascrew-fastening method. During this fixation process, a cathode currentcollector plate is electrically connected to an anode sideinterconnector of an adjacent fuel cell, and a start and an end partsare taken out as output terminals 16.

[0052] In an operation of a fuel cell power generation equipment, a lidof an air vent hole 15 shown in FIG. 4B, which also has a role of a fuelfeed hole, is removed, through which a liquid fuel such as an aqueousmethanol solution is filled up. Thus filled aqueous methanol solution isstably fed to an anode of a unit cell mounted on a bottom surface of thecontainer by penetration, whereas it is also stably fed to an anode of aunit cell mounted on a upper surface by sucking up with a suckingmaterial.

[0053] Since a cathode of each unit cell is in contact with ambient airthrough a net-like, a porous or a slit-like through hole, a cathodecurrent collector plate and a cathode diffusion layer, oxygen in air isfed by diffusion and water formed during power generation are dischargedby diffusion.

[0054]FIG. 6 shows an appearance of a fuel cell power generationequipment of the present invention. The equipment has a structure inwhich a fuel container 1 having air vent holes 15 functions as astructural body of power generation equipment and also has a pluralityof unit cells 13 fixed on its wall surface with a fuel cell fixing plate8, and both ends, electrically connected in series, are taken out asoutput terminals 16.

[0055] In power generation, carbon dioxide is formed by oxidizing a fuelin an anode side, that is, in a fuel container, and discharged tooutside of a fuel container through air vent holes having a gas/liquidseparation function and being impermeable for liquid. These air ventholes have a feature to ensure a stable operation of power generation byarranging a plurality of holes on a wall surface of a fuel container sothat at least one vent hole is kept unsealed from a liquid fuel in anyposition of the container during power generation.

[0056] A fuel cell power generation equipment in accordance with thepresent invention does not require any facility to compulsorily feed afuel or an oxidizing agent gas, and has a structure with only one layerof unit cell mounted on a wall surface of a container without adopting alaminated structure of multiple layers of cells with a separator inbetween, and further dose not need a compulsory cooling mechanism due toa sufficient heat radiation. Therefore, a structure with no power losscoming from auxiliary equipment, no need of a conductive separator forlamination and reduced number of parts can be obtained.

[0057] In a fuel cell using an aqueous methanol solution as a fuel,power is generated by directly converting a chemical energy possessed bymethanol to an electrical energy according to the followingelectrochemical reactions.

[0058] In an anode electrode side, an aqueous methanol solution feddissociates into carbon dioxide, hydrogen ions and electrons accordingto the formula (1).

CH₃OH+H₂O→CO₂30 6H⁺+6e ⁻  (1)

[0059] Hydrogen ions formed move from an anode to a cathode side in anelectrolyte membrane, and reacts with oxygen gas coming by a diffusionfrom air and electrons in accordance with the formula (2) forming wateron an electrode.

6H⁺+3/2O₂+6e ⁻→3H₂O  (2)

[0060] Therefore, a total chemical reaction accompanied with powergeneration is an oxidation of methanol by oxygen to form carbon dioxideand water, formally the same as in a flaming combustion of methanol asshown in the formula (3).

CH₃OH+3/2O₂→CO₂+3H₂O  (3)

[0061] An opening circuit voltage of a unit cell is about 1.2 V ataround the room temperature. However, the voltage is substantially0.85-1.0 V due to an effect of fuel penetration into an electrolytemembrane. A current density under load is selected so that the voltagein a practical operation under load becomes in the range of 0.3-0.6 V,though not specially limited. Therefore, in a practical application as apower source, a plurality of unit cells are used connected in series toprovide a prescribed voltage in accordance with a requirement of loadequipment.

[0062] An output current density of unit cell varies by effects of anelectrode catalyst, an electrode structure and others. However, it isdesigned so that a prescribed current can be obtained by effectivelyselecting an area of power generation part of a unit cell.

[0063] A supporting body composing a fuel cell power generationequipment in accordance with the present invention is characterized in afuel container to receive a liquid fuel, whose cross-sectional shape maybe square, circular or other any shape without any particularlimitation, so long as it has a shape which can mount a necessary numberof unit cells compactly. However, a cylindrical or a square shape ispreferable for a compact mounting of unit cells in a specified volume,due to a good mounting efficiency and a good processability in mountingof a power generation part of fuel cell.

[0064] There is no specific limitation in a material for supporting bodyso long as it is electrochemically inactive in a servicing environmentand has a durability, a corrosion resistance and a sufficient strengthwith a thin structure. A material for supporting body includes, forexample, polyethylene, polypropylene, poly(ethylene terephthalate),poly(vinyl chloride), polyacrylic resins and other engineering resins,electrically insulating materials thereof reinforced with variousfillers, carbon materials or stainless steels superior in corrosionresistance in a cell servicing environment, or ordinary iron, nickel,copper, aluminum or alloys thereof whose surfaces are treated to makecorrosion resistant and electrically insulating. In any case, there isno limitation so long as it has strength to support a shape, corrosionresistance and electrochemical inactivity.

[0065] Inner part of a fuel cell supporting body is used as a space forfuel storage and transport. A sucking material filled in an inner partof a cylindrical supporting body to stabilize feeding of a fuel may beany type so long as it has a small contact angle with a aqueous methanolsolution and is electrochemically inactive and corrosion resistant, andpowdery or fibrous material is preferable. For example, fibers made ofglass, alumina, silica-alumina, silica, non-graphite carbon andcellulose or water absorptive polymer fibers are materials with a lowpacking density and a superior retention for an aqueous methanolsolution.

[0066] As an anode catalyst which composes a power generation part, fineparticles of platinum and ruthenium or platinum/ruthenium alloysdispersed and supported on carbon powder, whereas, as a cathodecatalyst, fine particles of platinum dispersed and supported on carboncarrier are materials to be easily manufactured.

[0067] An anode and a cathode catalysts in a fuel cell of the presentinvention are not specially limited so long as they are used in a usualdirect methanol fuel cell, and it is preferable to use a catalyst of theabove described noble metal components added with a third componentselected from iron, tin, rare earth elements and the like, to stabilizeor extend a life of electrode catalyst.

[0068] As an electrolyte membrane, a hydrogen ion conductive membrane isused although not limited. Typical material includes sulfonated oralkylenesulfonated fluoropolymers such as perfluorocarbon type sulfonicacid resin, poly(perfluorostyrene) type sulfonic acid resin,polystyrenes; polysulfones; polyethersulfones; polyetherethersulfones;polyetheretherketones; and other sulfonated hydrocarbon polymers.

[0069] Materials with a small methanol permeation among theseelectrolyte membranes are preferable because they can raise acoefficient of utilization of fuel with little lowering of cell voltageby fuel crossover, and generally enable to operate a fuel cell at thetemperature not higher than 90° C. Fuel cell which can be operated atfurther higher temperature range can also be obtained by using acomposite electrolyte membrane prepared by a heat resistant resinmicro-dispersed with a hydrogen ion conductive inorganic material suchas hydrates of tungsten oxide, zirconium oxide and tin oxide;tungstosilicic acid; molybdosilicic acid; tungstophosphoric acid andmolybdophosphoric acid.

[0070] In any of these cases, higher levels of miniaturization andlonger power generation time, which are the effects of the presentinvention, are attained by using an electrolyte membrane having a highhydrogen ion conductivity and a low methanol permeability, due to ahigher coefficient of utilization of fuel.

[0071] The above described hydrated type of acidic electrolyte membranesmay, in general, have problems such as a membrane deformation induced bya difference in swelling between dry and wet conditions and aninsufficient mechanical strength with a membrane having a sufficientlyhigh ion conductivity. In these cases, it is effective methods forenhancing a reliability of cell performance to use a fiber with superiormechanical strength, durability and heat resistance as a core materialin a form of non-woven fabric or woven fabric or to add these fibers asreinforcing fillers in manufacturing an electrolyte membrane.

[0072] In addition, a membrane of polybenzimidazoles doped with sulfuricacid, phosphoric acid, sulfonic acids or phosphonic acids may also beused to reduce a fuel permeability of an electrolyte membrane.

[0073] As another example instead of the above described method, a powergeneration part of unit cell can be prepared, for example, by thefollowing processes. That is, a unit cell is prepared through thefollowing processes:

[0074] (i) A process to coat a conductive interconnector on anelectrically insulating outer circumferential surface of a liquid fuelcontainer and make a wall surface of an anode junction part porous bythrough holes;

[0075] (ii) A process to prepare a past by adding and dispersing asolution which is prepared by dissolving an anode catalyst and anelectrolyte resin in a volatile organic solvent in advance, then form anelectrode by coating the past on a notched porous part of a liquid fuelcontainer in a certain thickness of 10 -50 μm;

[0076] (iii) A process to mask the coated anode part, coat a gasket forsealing on the notched part, then join to a fuel container.

[0077] (iv) A process subsequently to coat an electrolyte solution,prepared by dissolving in a volatile organic solvent in advance, on thenotched part in contact with an anode electrode so that a thicknessafter forming a membrane becomes 20-50 μm;

[0078] (v) A process then to prepare a past as a binder by mixing asolution which is prepared by dissolving a. cathode catalyst and anelectrolyte resin in a volatile organic solvent in advance, and form anelectrode by coating the past on an electrolyte membrane in a certainthickness of 10-50 μm;

[0079] (vi) A process further to prepare a past by mixing carbon powderand a prescribed amount of water repellent dispersing agent, forexample, aqueous. dispersion of fine particles ofpolytetrafluoroethylene, and form a diffusion layer by coating the paston the notched part in contact with a surface of cathode electrode in anoutside of the electrode.

[0080] In the process (iv) among these processes, it is important toseal the electrolyte membrane part by closely contacting or adheringusing an adhesive with the gasket by making an electrolyte membrane partlarger than a cathode area.

[0081] A cathode current collector is prepared by mounting a conductiveporous material or a net in a cathode side diffusion layer part of thusobtained unit cell, which is electrically connected to an interconnectorfrom an adjacent unit cell, and terminals are taken out from both endsconnected in series. It is an effective method for preventing floodingof water formed during a fuel cell operation, to provide a diffusionlayer in a cathode side.

[0082] In addition, in manufacturing a diffusion layer, in a case when awater repellent aqueous dispersing agent contains a surfactant which isa poisonous component for platinum catalyst or platinum/ruthenium alloycatalyst, it is an effective method to coat a past prepared by mixingcarbon powder. and a certain amount of water repellent dispersing agent,for example, aqueous dispersion of fine particles ofpolytetrafluoroethylene on one side of a conductive woven fabric such asa carbon fiber, then mount the fabric so that the coated side is incontact with a cathode after burning at a decomposition temperature ofthe surfactant in advance, and use the woven fabric of carbon fiber as acathode current collector.

[0083] In any case, there is no special limitation in a manufacturingmethod so long as a unit cell is manufactured by providing an anode, anelectrolyte membrane, a cathode and a diffusion layer in layers in thisorder, and forming sufficient reaction interfaces betweenanode/electrolyte membrane and cathode/electrolyte membrane.

[0084] Further, a cell composition without requiring a diffusion layermay be prepared by coating a past prepared by adding a prescribed amountof a water repellent dispersing agent, for example, fine particles ofpolytetrafluoroethylene to a solution prepared by dissolving cathodecatalyst, electrolyte membrane and electrolyte in a volatile organicsolvent in advance in forming a cathode.

[0085] A high voltage intended by the present invention can be attainedby using a liquid fuel container as a platform, preparing multiple unitcells composed of an anode, an electrolyte membrane and a cathode on itsouter circumferential surface, and connecting each unit cell in serieswith a conductive interconnector. In addition, a compact power sourcecan also be attained, which can be operated without using auxiliaryequipment to compulsorily feed a fuel and an oxidizing agent or withoutusing auxiliary equipment to compulsorily cool a fuel cell, and providea long time continuous power generation by using a aqueous methanolsolution having a high volume energy density as a liquid fuel.

[0086] This compact power source can be used as a built-in driving unitfor a cellular phone, notebook-type personal computer or a mobile videocamera, and can be continuously used for a long time by sequentiallyfeeding a fuel prepared in advance.

[0087] Further, it is also effective to use this compact power source asa battery charger, by connecting it with a charger of, for example, asecondary battery driven cellular phone, notebook-type personal computeror mobile video camera, and by mounting it in a part of container casethereof, to remarkably reduce a frequency of fuel feeding compared withthe above described case. In this case, the portable electronic deviceis driven with a secondary battery by removing the fuel cell powergeneration equipment from a container case when in service, whereas whennot in service, the fuel cell power generation equipment is put in thecase and the compact fuel cell power generation equipment built in thecase is connected via a charger to charge the secondary. Thus, volume ofa fuel tank can be enlarged and a frequency of fuel feeding can beremarkably reduced.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0088] The present invention will be described based on the Exampleshereinbelow.

Comparative Example 1

[0089]FIG. 7 is a cross-sectional drawing showing a separator structurebased on a conventional structure. FIG. 7A shows an in-plane structureand a longitudinal cross-sectional drawing of one part and FIG. 7B showsan in-plane structure and a lateral cross-sectional drawing of the otherpart, FIG. 8 and FIG. 9 show a laminated composition of cell and acomposition of cell holder, respectively, FIG. 10A shows a structure ofpower source system composed of 2 sets of laminated unit cells 18 inseries and a fuel container attached, and FIG. 10B shows across-sectional structure of connection between a fuel cell at alamination end and a fuel container.

[0090] A graphitized carbon plate of 16 mm width×33 mm length×2.5 mmthickness was used for a separator 81. An inner manifold 82 of 10 mmwidth×4 mm length is mounted at a bottom of the separator 81, and a fuelfeeding channel was provided to connect a manifold 82 and upper surfaceof a separator 81 by forming a rib part 54 by making channels of 1 mmwidth×0.8 mm depth×23 mm length at 1 mm interval as shown by numeral 84in FIG. 7B of a lateral cross-sectional drawing of a separator.

[0091] On the other hand, in other surface of the separator, a feedingchannel for an oxidizing agent to connect a side surface of a separator21 was made by forming a rib part 84 composed of channels of 1 mmwidth×1.4 mm depth×16 mm length at 1 mm interval in rectangulardirection to the opposite surface, as shown in FIG. 7B and alongitudinal cross-sectional drawing 83 of a separator.

[0092] As an anode layer, a porous membrane of about 20 μm thickness wasformed on a polyimide film by screen printing of a slurry, prepared bymixing catalyst powder of 50% by weight of fine particles ofplatinum/ruthenium alloy, in an atomic ratio of platinum/ruthenium being1/1, dispersed and supported on carbon carrier, 30% by weight ofperfluorocarbon sulfonic acid electrolyte (trade name: Nafion 117 fromDuPont Inc.) as a binder, and water/alcohol mixed solvent(water:isopropanol:n-propanol is 20:40:40, ratio by weight).

[0093] As a cathode layer, a porous membrane of about 25 μm thicknesswas formed on polyimide film by screen printing of a slurry, prepared bymixing 30% by weight of fine powder catalyst of platinum supported oncarbon carrier and an electrolyte in a water/alcohol mixed solvent as abinder.

[0094] Thus prepared anode and cathode porous membranes were cut outeach in 10 mm width×20 mm length to obtain an anode and a cathodelayers.

[0095] Next, manifold opening part 86 was made in Nafion 117 with 16 mmwidth×33 mm length×50 μm thickness, as an electrolyte membrane.

[0096] An anode layer surface was joined to a power generation part ofthe above electrolyte membrane, after being penetrated with about 0.5 mlof a 5% by weight aqueous alcohol solution of Nafion 117 (a mixedsolvent of water:isopropanol:n-propanol is 20:40:40, ratio by weight,from Fluka Chemika Ltd.), followed by drying at 80° C. for 3 hours underabout 1 kg of load. Then, a cathode layer surface was joined to theelectrolyte membrane so that the electrolyte membrane was overlappedwith the above joined anode layer, after being penetrated with about 0.5ml of a 5% by weight of the above described aqueous alcohol solution ofNafion 117, followed by drying at 80° C. for 3 hours under about 1 kg ofload to prepare MEA 9.

[0097] Next, a poly(ethylene terephthalate) liner 92 with 250 μmthickness and a neoprene gasket 10 with 400 μm thickness were preparedby making manifold opening part 86 and power generation opening part 85of the same size as in the separator 81.

[0098] Then, a carbon sheet was formed by adding an aqueous dispersionof water repellent fine particles of polytetrafluoroethylene (Teflondispersion D-1 from Daikin Industries Ltd.) to carbon powder so that aconcentration of the water repellant became 40% by weight after firing,and mixing to a paste, coating the paste on one surface of a carbonfiber woven fabric having about 350 μm thickness and a porosity of 87%in a thickness of about 20 μm, drying at room temperature and firing at270° C. for 3 hours. Thus obtained sheet was cut out to the same sizeand shape as of the above described MEA electrode to prepare a diffusionlayer 11.

[0099] Then, a fuel sucking material 5 made of pulp paper, consisting ofa channel insertion part 88 in a fuel electrode side of separator 81 anda manifold insertion part 87, was prepared.

[0100] These parts were laminated, as shown in FIG. 8, in the order of aseparator 81, a sucking material 5, a liner 92, a gasket 10, MEA 9, adiffusion layer 11, a liner 92 and a separator 81 as one unit, and 14units were piled up, followed by pressing at about 5 kg/cm² to obtain alaminated cell 94. Said laminated cell 94 was fixed as shown in FIG. 10A, with a fastening band 17 made of fluorocarbon rubber (Viton fromDuPont Inc.), using a SUS 316 holder 105, having a structure shown inFIG. 9, whose surface was insulated with an epoxy resin (Flep from TorayThiokol Co., Ltd.).

[0101] A fuel container 1 was prepared with polypropylene having outerdimensions of 33 mm height×85 mm length×65 mm width×2 mm side wallthickness and having a laminated cell mounting part 103.

[0102] As shown in FIG. 10 B, in a center part of fuel container 1, anair vent tube 51 with a screw lid 52 having a gas permselective functionwhich mounted a porous polytetrafluoroethylene membrane, having astructure similar to that shown in FIG. 4A as a gas/liquid separationmembrane 50, was provided as an air vent hole 15, and inside of the fuelcontainer is filled with an aqueous methanol solution 12 as a fuel. Thusprepared two laminated cells having a structure as shown in FIG. 10Bwere connected to a fuel cell mounting part 103 to obtain a power sourcehaving a structure as shown in FIG. 10A.

[0103] The above power source has a size of about 33 mm height×120 mmlength×65 mm width, and is equipped with a fuel container having asurface area of power generation part of about 2 cm² and a volume ofabout 150 ml. The power source showed a voltage of 5.7 V at theoperation temperature of 50° C. and the load current of 0.2 A, and alsoshowed a voltage of 11.8 V when operated with blasting with a fan towhole surface of openings in a side wall of power source composed ofside channels in an air electrode side of separator. This is consideredto happen because oxygen is not fed sufficiently by air diffusion usinga side channel structure with air electrode of a separator when a powersource is loaded. A volume output density of this power source was about4.4 W/l without using an air vent fan and about 9.2 W/l using the airvent fan.

[0104] When a fuel container was filled with 150 mm of a 10% by weightof aqueous methanol solution, and the power source was operated at theoperation temperature of 50° C. and the load current of 0.2 A with ablasting fun, an output voltage continued to show 11.8 V for about 4.5hours, then rapidly dropped. Therefore, a volume energy density in anoperation when the fuel of a 10% by weight of aqueous methanol solutionwas filled was 41 Wh/l using an air vent fan.

[0105] This fuel cell power generation equipment has a structure inwhich a liquid fuel is sucked up from a manifold in the bottom oflaminated cell and carbon dioxide formed by an oxidation of a fuel isdischarged from the top of laminated cell. Therefore, it has a problemthat power generation can no longer be continued when it is placedupside down or turns sideways during operation.

EXAMPLE 1

[0106]FIG. 11 shows a structure of MEA in accordance with this Example.MEA is formed by joining an anode layer 22 and a cathode layer 23 usingan electrolyte resin as a binder so that they are overlapped with bothsides of an electrolyte membrane 21.

[0107] As an anode layer, a porous membrane of about 20 μm thickness wasformed by screen printing of a slurry, prepared by 50% by weight of finepowder catalyst of platinum/ruthenium alloy with an atomic ratio ofplatinum/ruthenium being 1/1, dispersed and supported on carbon carrier,and 30% by weight of perfluorocarbone sulfonic acid electrolyte (Nafion117) in a water/alcohol mixed solvent (water:isopropanol n-propanol is20:40:40 ratio by weight) as a binder.

[0108] As a cathode layer, a porous membrane of about 25 μm thicknesswas formed by screen printing of a slurry, prepared by 30% by weight offine powder catalyst of platinum supported on carbon carrier and anelectrolyte in a water/alcohol mixed solvent as a binder.

[0109] The above-mentioned anode and cathode porous membranes were cutout each in 10 mm width×20 mm length to obtain an anode layer 22 and acathode layer 23. Nafion 117 electrolyte membrane with the thickness of50 μm was cut out in 20 mm width×30 mm length and a surface of the anodelayer was joined to a center part of the electrolyte membrane, afterbeing penetrated with about 0.5 ml of a 5% by weight aqueous alcoholsolution of Nafion 117 (a mixed solvent of water:isopropanol:n-propanolis 20:40:40 ratio by weight, from Fluka Chemika Ltd.), followed bydrying at 80° C. for 3 hours under the load of about 1 kg.

[0110] Then, a surface of cathode layer was joined to a center part ofthe electrolyte membrane so that the layer was overlapped with an anodelayer 22 joined in advance, after being penetrated with about 0.5 ml ofa 5% by weight aqueous alcohol solution of Nafion 117 (from FlukaChemika Ltd.), followed by drying-at 80° C. for 3 hours under the loadof about 1 kg to prepare MEA.

[0111] Subsequently, a carbon sheet was prepared by adding an aqueousdispersion of water repellent fine particles of polytetrafluoroethylene(Teflon dispersion D-1 from Daikin Industries Ltd.) so that aconcentration of the repellant became 40% by weight after firing tocarbon powder and mixing to a paste, coating the paste on one surface ofa carbon fiber woven fabric having the thickness of about 350 μm and theporosity of 87%, to the thickness of about 20 μm, drying at roomtemperature and firing at 270° C. for 3 hours. Thus obtained sheet wascut out to the same size and shape as of the above described MEAelectrode to prepare a diffusion layer.

[0112] Next, a method for mounting a fuel cell composed of MEA on anouter circumferential surface of fuel container will be explained usingFIG. 13 showing a cross-sectional structure of a fuel cell powergeneration equipment.

[0113] A fuel sucking material 5 made of a glass fiber mat with thethickness of 5 mm and the porosity of about 85% was mounted on an innerwall surface of a fuel container 1, made of rigid poly(vinyl chloride)having the outer dimensions of 65 mm width×135 mm length×25 mm heightand the wall thickness of 2 mm.

[0114] Eighteen fuel cell mounting parts 2, having the dimensions of 21mm width×31 mm length×0.5 mm depth, were equipped in each of a top and abottom of outer wall surface of a fuel container 1. A diffusion hole 3was made by preparing slits of 1 mm width×10 mm length in an interval of1 mm in each fuel cell mounting part 2 in contact with an anode. Inthese slits, a carbon fiber mat with the porosity of 85% was filled soas to contact with a fuel sucking material 5 mounted at inner wallsurface of a fuel container.

[0115] In an outer surface of the slit, an electroless nickel platedlayer with the thickness of about 50 μm was provided as aninterconnecter 4 to electrically connect to a cathode current collector7 of an adjacent fuel cell. Air vent holes 15, having a gas/liquidseparation function with the same structure as shown in FIG. 4A, wereprovided at four corners of a top and a bottom of the fuel containerthus obtained.

[0116] Then, a fuel cell fixing plate 8 is made using rigid poly(vinylchloride) with the thickness of 2.0 mm, the same as a fuel container 1,and a slit of 1.0 mm width×20 mm length was provided on its surface incontact with a cathode of each fuel cell in a rectangular direction tothe slit provided in a fuel cell mounting part 2 as a diffusion hole 3.On this fuel cell fixing plate 8, a cathode current collector 7 made ofnickel with a slit, which was formed in the same shape as its slit partso as to connect to an interconnector 4 of an adjacent fuel cell, wasfixed.

[0117] In mounting the above described MEA 9 on this fuel container,each cell was fixed to a fuel container with a fuel cell fixing plate 8,after arranging MEA 9, having seal gaskets 10 on both surfaces, in afuel cell mounting part 2, and a diffusion layer 11 in its cathode side.In this fixation process, a cathode current collector 7, which wasarranged in advance in a cathode side surface of the fuel cell fixingplate 8, electrically connects a cathode and an interconnector 4 from ananode of adjacent fuel cell, and connects each cell in series. Endparts, connecting each fuel cell, are taken out as cell terminals 16from an interface of the fuel cell fixing plate 8 and the fuel containerto an outside of the container. FIG. 12 shows an appearance of a fuelcell power generation equipment in accordance with this Example.

[0118] On an upper and a bottom surfaces of fuel container 1 having airvent holes 15, 36 unit cells 13 are mounted by the fuel cell fixingplate 8, and an output terminal 16 is provided. A 10% by weight ofaqueous methanol solution 12 is charged into the container through oneof the air vent holes 15 of the fuel container thus mounted with fuelcells. This fuel cell has the dimensions of about 65 mm width×135 mmlength×29 mm height and the fuel containing volume of about 150 mm. Apower generation equipment has the power generation surface area of 2cm² and is composed of 36 series.

[0119] An output voltage of this fuel cell power generation equipment inoperation was 12.2 V at the temperature of 50° C. and the load currentof 200 mA. A continuous power generation was possible for about 4.5hours in the operation by filling a 10% by weight of aqueous methanolsolution and at the load current of 200 mA. An output density of thisfuel cell power generation equipment was about 9.6 W/l and a volumeenergy density per litter fuel was about 50 Wh/l.

[0120] In addition, no change in an output voltage or no pressure risein a fuel container was observed even if the power generation equipmentwas operated in the positions of upside down or turning sideways.

[0121] As described above, a high voltage type compact fuel cell of 12volt class can be attained without laminating with a separator inbetween by mounting multiple fuel cells on an outer wall surface of aliquid fuel container and connecting in series by an interconnector. Inthis case, a power source without requiring auxiliary equipment such asa fuel feed pump and a fan for cathode gas became possible by contactingan anode and an inner part of container using a liquid fuel suckingmaterial in the anode side and exposing a cathode to ambient air througha diffusion layer.

[0122] In particular, by arranging air vent holes having a gas/liquidseparation function on a plurality of surfaces of a fuel container, anormal power generation became possible at any position of a fuel cell,and essential characteristics for a portable power generation equipmentcould be attained.

Comparative Example 2

[0123] A compact fuel cell of low voltage type using a separator will beexplained using FIG. 14. Using the same materials and sizes as inComparative Example 1 for separator, sucking material, liner, gasket,MEA and diffusion layer as components of a cell, a laminated cell 23 wasprepared by the same procedure as in Comparative Example 1 so as to havefour unit cells. This laminated cell was inserted to a cell holder 105,and fastened with a fastening band 17 made of fluorocarbon rubber in thesame manner as in Comparative Example 1.

[0124] A fuel cell was made of polypropylene with the outer dimensionsof 33 mm height×16 mm length×65 mm width and the wall thickness of 2 mm.

[0125] As shown in FIG. 14, air vent holes 15 mounted with porouspolytetrafluoroethylene membranes having the same structure as shown inFIG. 4A were provided at the central part of an upper surface of a fuelcontainer 1.

[0126] A power source was prepared using thus prepared laminated cell 23combined with a fuel container 1 with the same composition as inComparative Example 1. Thus obtained power source has the dimensions ofabout 33 mm height×82 mm length×16 mm width, with the surface area ofpower generation part of about 2 cm² and a fuel container 1 having thevolume of about 20 ml.

[0127] The power source shows 0.58 V at the operation temperature of 50°C. and the current load of 0.2 A, and 1.26 V when operated by blastingwith a fan to the whole area of opening part in a side wall of the powersource composed of side channels in an air electrode side of aseparator. It is considered to happen because oxygen was not fed by airdiffusion with the air electrode side channel structure of a separatorunder a loaded power source. A volume output density of this powersource was about 2.7 W/l when an air vent fan was not used and about 5.8W/l when the air vent fan was used.

[0128] An output voltage was 1.26 V in the operation by filling 20 ml ofa 10% by weight of aqueous methanol solution, using a blast fan at theoperation temperature of 50° C. and the load current of 0.2 A. Thevoltage continued for about 5 hours then rapidly dropped. Therefore, avolume energy density per litter fuel of a 10% by weight of aqueousmethanol solution was 29 Wh/l when a blast fan was used.

[0129] This fuel cell power generation equipment has a structure inwhich a liquid fuel is sucked up from a manifold in the bottom oflaminated cell and carbon dioxide formed by an oxidation of a fuel isdischarged from the top of laminated cell. Therefore, it has a problemthat power generation can no longer be continued when it is placedupside down or turns sideways during operation.

EXAMPLE 2

[0130]FIG. 15 shows a cross-sectional structure of a rectangular typeand low voltage type of power generation equipment using methanol as afuel in accordance with this Example, and FIG. 16 shows outline of amounting method for fuel cells. MEA was prepared by an almost similarmethod as in Example 1. A porous membrane of about 20 μm thickness wasformed on a polyimide film with the dimensions of 30 mm width×50 mmlength by screen printing using a slurry, which was prepared by mixing acatalyst powder of 50% by weight of platinum/ruthenium alloy fineparticles, an atomic ratio of platinum/ruthenium being 1/1, dispersedand supported on carbon carrier, 30% by weight of perfluorocarbonsulfonic acid electrolyte (Nafion 117) as a binder and a water/alcoholmixed solvent (water:isopropanol:n-propanol was 20:40:40, ratio byweight), followed by drying at 90° C. for 3 hours to get an anode porouslayer.

[0131] A porous cathode layer of about 25 μm thickness was formed on apolyimide film with the dimensions of 30 mm width×50 length by screenprinting of a slurry, which was prepared by mixing a catalyst powder of30% by weight of fine platinum powder supported on carbon carrier, anelectrolyte as a binder and a water/alcohol mixed solvent, followed bydrying at 90° C. for 3 hours.

[0132] Thus prepared anode and cathode porous membranes were cut outeach in 10×10 mm size to obtain an anode layer and a cathode layer.Sulfonated polyetherethersulfone membrane of 28 mm width×56 mm length×50μm thickness having 790 g/eq was used as an electrolyte.

[0133] Firstly, eight anode layers were penetrated with about 0.5 ml ofa 5% by weight aqueous alcohol solution of Nafion 117 (from FlukaChemika Ltd.) in each surface, then arranged evenly on one surface of anelectrolyte membrane, followed by drying of each electrode at 80° C. for3 hours under the load of about 1 kg.

[0134] Then, a cathode layer surface was penetrated with about 0.5 ml ofa 5% by weight aqueous alcohol solution of Nafion 117, then arranged onthe opposite side surface of the above electrolyte membrane joined withan anode so as to be overlapped with the anode layer, followed by dryingat 80° C. for 3 hours under the load of about 1 kg on each cell toprepare MEA.

[0135] As shown in FIG. 16, a fuel container 1 was made of rigidpoly(vinyl chloride), having the outer dimensions of 22 mm width×79 mmlength×23 mm height and wall thickness of 2 mm. As shown in FIG. 15 of across-sectional structure, four fuel cell mounting parts 2, having thedimensions of 16 mm width×16 mm length×0.5 mm depth, were provided oneach of an upper and a bottom surfaces of the fuel container 1. A slitof 1 mm width×10 mm length through an inside of the fuel container 1 wasprovided as a diffusion hole 3, in the central part of fuel cellmounting parts 2 with the size of 10 mm width×10 mm length.

[0136] In an outer surface of this mounting parts 2, a nickel layer withthe thickness of about 0.1 mm was formed by an electroless platingmethod as an interconnector 4 in order to electrically connect to anadjacent fuel cell. A fuel sucking material 5 was provided by adhering aglass fiber mat with the thickness of 1 mm thickness and the porosity ofabout 70% on an inner wall of the fuel container 1, and further a lowdensity fuel retaining layer 18 filled with a glass fiber was providedin the container so as to make a porosity about 85%. Eight air ventholes 15, with a structure as shown in FIG. 4A and an inner diameter of2 mm, were provided at corners of an upper and a bottom surfaces of thefuel container 1.

[0137] As shown in FIG. 16, a fuel cell fixing plate 8 as a holdingplate for a fuel cell was prepared using rigid poly(vinyl chloride) withthe dimensions of 22 mm width×79 mm length×1 mm thickness, and a slit of1 mm width×10 mm length was provided in its surface in contact with acathode of each fuel cell in a rectangular direction to the slit of afuel cell mounting part 2 of fuel container 1, and also air vent holemounting holes 19 were provided at the four corners.

[0138] A cathode current collector 7 made of nickel with the thicknessof 0.2 mm having a slit was mounted on a fuel cell fixing plate 8 toconnect to an interconnector in an anode side of an adjacent fuel cell.

[0139] The fuel cell of this Example was prepared by laminating an anodeside gasket made of neoprene rubber, MEA 9, a cathode side diffusionplate 11, a cathode side gasket 10 made of neoprene rubber and a fuelcell fixing plate 8 in this order as shown in FIG.16, and said fixingplate was fixed to a fuel container 1 by screwing its peripheral part.

[0140] Output terminals 16 were made by connecting an anode sideterminal 6 and a cathode side terminal 6 mounted in an upper and abottom sides of the fuel container 1 each in parallel. Thus obtainedfuel cell power generation equipment has the outer dimension of 22 mmwidth×79 mm length×27 height and the power generation area of 1 cm², andcomposed of four series×two parallel fuel cells.

[0141] A volume of the fuel container 1 was about 20 ml. After filling a10% by weight of aqueous methanol solution in the fuel container throughan air vent hole 15, the fuel cell was operated at the operationtemperature of 50° C. and the load current of 200 mA to give an outputvoltage of 1.3 V. A continuous power generation was also carried outafter filling with 20 ml of a 10% aqueous methanol solution at the loadcurrent of 200 mA to give a stable voltage for about 5 hours with anoutput voltage of 1.3 V. An output density of this cell was about 5.5W/l and a volume energy density per litter fuel was about 28 Wh/l.

[0142] During the operation, no change in an output voltage or nopressure rise in a fuel container was observed even if the powergeneration equipment was operated in the positions of upside down orturning sideways.

[0143] Thus, a compact fuel cell of 1.3 volt class could be attained bymounting multiple fuel cells on one outer wall surface of a liquid fuelcontainer, connecting in series with an interconnecter, and connectingthe series cell groups mounted on multiple surfaces in parallel, withoutlaminating with a separator in between. In this case, a power source wasobtained without requiring any auxiliary equipment such as a fuel feedpump or a fan for cathode gas, by contacting an inner part of thecontainer and an anode with a liquid fuel sucking material in an anodeside and exposing a cathode to ambient air through a diffusion layer.

[0144] Further, shaking of the liquid fuel during operation could bereduced by filling inside of a fuel container with a low density fuelsucking material. In particular, by arranging air vent holes having agas/liquid separation function on a plurality of surfaces of a fuelcontainer, a normal power generation became possible at any position ofa fuel cell, and essential characteristics for a portable powergeneration equipment could be attained.

EXAMPLE 3

[0145] In this Example, a fuel cell with a metal fuel container coatedwith epoxy resin as a platform will be described.

[0146] MEA and a cathode side diffusion layer were prepared in the sameway as in Example 2A. A fuel container made of SUS 304 was prepared withthe outer dimensions of 22 mm width×79 mm length×23 mm height and thethickness of 0.3 mm, as shown in FIG. 17. The container is composed of aframe and an upper and a bottom lids having 4 faces of press formed fuelcell mounting parts 2 with the dimensions of 16 mm width×16 mmlength×0.5 mm depth.

[0147] A slit of 0.5 mm width×10 mm length was provided by punching as adiffusion hole 3 in a part having the size of 10 mm width×10 mm lengthin the center of a fuel cell mounting part 2. Air vent holes 15 with aninner diameter of 1 mm made of SUS 304 were mounted without using agas/liquid separation membrane in corner parts of an upper and a bottomlids. Using these parts, a fuel container 1 was prepared byweld-sealing, after filling the container with a fuel sucking materialmade of glass fiber mat having the porosity of about 80%.

[0148] An insulation layer 20 was formed by coating a liquid epoxy resincoating material (Flep from Toray Thiokol Co. Ltd.) on an outer surfaceof fuel container 1 in a thickness of 0.1 mm, followed by thermalcuring. A surface of fuel cell mounting part 2 was electroless platedwith nickel as an interconnecter 4 in an anode side in the same shape asin Example 2.

[0149] A slit of 1 mm width×10 mm length was provided using rigidpoly(vinyl chloride) with the dimensions of 22 mm width×79 mm length×1mm thickness in a fuel cell fixing plate similar to Example 2, in asurface contacting a cathode of each fuel cell in a rectangulardirection to the slit in a fuel cell mounting part 2, and air vent holes15 were also provided at the four corners. Using this slit, a cathodecurrent collector 7 made of nickel with a slit having the thickness of0.2 mm was mounted to connect to an interconnecter 4 in an anode side ofan adjacent fuel cell.

[0150] The fuel cell of this Example was obtained, in the same way as inExample 2, by laminating anode side gasket made of fluorocarbon rubber,MEA, cathode side gasket made of fluorocarbon rubber, cathode sidediffusion layer and fuel cell fixing plate in this order, and fixed to afuel container by fastening a peripheral part of said fixing plate witha heat shrinkable 100 μm thick resin tube with a slit. Output terminalswere obtained by connecting, each in series, an anode side terminals anda cathode side terminals mounted on an upper and a bottom sides of afuel container.

[0151] Thus obtained fuel cell power generation equipment had the outerdimensions of 22 mm width×79 mm length×27 height and the powergeneration area of 1 cm², and composed of eight series of fuel cells. Avolume of the fuel container was about 38 ml. After filling a 10% byweight of aqueous methanol solution as a fuel with a syringe through airvent holes of this fuel container, the fuel cell power generationequipment was operated at the operation temperature of 50° C. and theload current of 100 mA to give an output voltage of 2.6 V.

[0152] In addition, a continuous power generation was carried out at theload current of 100 mA after filling the fuel container with about 37 mlof a 10% by weight of aqueous methanol solution, a stable voltage wasobtained at an output of 2.6 V for about 4 hours. An output density ofthis fuel cell power generation equipment under this condition was about5.5 W/l and a volume energy density per litter fuel was about 22 Wh/l.

[0153] With this fuel cell, no change in an output voltage, no leakageof the liquid fuel or no pressure rise in a fuel container was observedeven if the power generation equipment was operated in the positions ofupside down or turning sideways.

[0154] Thus, a compact fuel cell of 2.6 volt class could be attained bymounting multiple fuel cells on one outer wall surface of a liquid fuelcontainer, connecting in series with an interconnecter and connectingthe series cell groups mounted on multiple surfaces in parallel, withoutlaminating with a separator in between. In this case, a power sourcecould be obtained without requiring any auxiliary equipment such as afuel feed pump or a fan for cathode gas, by contacting an inner part ofthe container and an anode with a liquid fuel sucking material in ananode side and exposing a cathode to ambient air through a diffusionlayer.

[0155] A fuel container of this Example was characterized in that alarge volume can be obtained because the container is composed of ametal material with an insulation treated surface. In addition, it wasalso possible to prevent a leakage of liquid fuel and to provide astable power generation in any position of the container during powergeneration by filling an inside of the container with a relatively lowdensity of fuel sucking material and by providing only small open holeswithout having a gas/liquid separation function. It also became possiblein production of said power generation equipment, to easily fix eachfuel cell using a heat shrinkable resin tube.

EXAMPLE 4

[0156] In this Example, a polygonal cylinder type methanol fuel cellpower generation equipment with a metal fuel container coated with epoxyresin as a platform will be described.

[0157] MEA with the outer dimensions of 24 mm width×29 mm length and theouter dimensions of electrode of 20 mm width×25 mm length was preparedin the same way as in Example 2. A cathode diffusion layer with theshape of 20 mm width×25 mm length was also prepared in the same way asin Example 2.

[0158] The fuel cell was a hexagonal cylinder having the dimensions of28 mm side×190 mm height and the wall thickness of 0.3 mm, and composedof press formed fuel cell mounting part with the dimensions of 24 mmwidth×29 mm length×0.5 mm depth in each side and hexagonal upper andbottom lids.

[0159] Slits of 0.5 mm width×25 mm length were punched at the intervalof 0.5 mm, in the central part of 20 mm width×25 mm length of a fuelcell mounting part. Six air vent holes having a gas/liquid separationfunction and the inner diameter of 2 mm were provided in peripheralparts of upper and bottom lids, as shown in FIG. 4. Upper and bottomlids were weld-sealed, after mounting a glass fiber mat having thethickness of 5 mm and the porosity of about 85% in an inner wall part ofthe hexagonal cylinder. An outer surface of a fuel container was coatedwith a liquid epoxy resin coating material (Flep from Toray Thiokol Co.,Ltd.) in the thickness of 0.1 mm, followed by thermal curing andelectroless plating with nickel as an interconnecter in an anode side,in the same shape as in Example 2.

[0160] Similar to Example 2, a fuel cell fixing plate 8 as a holdingplate for a fuel cell was prepared using rigid poly(vinyl chloride) withthe dimensions of 28 mm width×190 mm length×1 mm thickness, and a slitof 0.5 mm width×20 mm length was provided at the interval of 0.5 mm inits surface in contact with a cathode of each fuel cell in a rectangulardirection to the slit in the notched part of fuel container. Using theseslits, a cathode current collector made of nickel having slits with thethickness of 0.2 mm was mounted in order to connected to aninterconnector in an anode side of an adjacent fuel cell.

[0161] The fuel cell of this Example was obtained, in the same way as inExample 2, by laminating anode side gasket made of fluorocarbon rubber,MEA, cathode side gasket made of fluorocarbon rubber, cathode sidediffusion layer and fuel cell fixing plate in this order, and fixed to afuel container by fastening a peripheral part of a fuel cell fixingplate with a heat shrinkable 100 μm thick resin tube with a slit. FIG.18 shows thus obtained fuel cell power generation equipment.

[0162] On an outer wall of a hexagonal cylinder type fuel container 1having six air vent holes each in an upper and a bottom parts, 36 unitcells 13 were mounted, which were each connected in series and outputterminal 16 was taken out from the fuel container 1. Thus obtained fuelcell power generation equipment has hexagonal cylinder with the outerdimensions of about 28 mm side and about 190 mm height and the powergeneration area of 5 cm² and a direct current power generating equipmentcomposed of 36 series. A volume of the fuel container was about 300 ml.

[0163] After filling a 10% by weight of aqueous methanol solution in afuel container, a continuous power generation was carried out at theload current of 500 mA to give a stable voltage for about 4 hours at theoutput voltage of 12.1 V. An output density at this condition was about15 W/l and a volume energy density per litter fuel was about 60 Wh/l.

[0164] With this fuel cell, no change in an output voltage, no leakageof the liquid fuel or no pressure rise in a fuel container was observedeven if the power generation equipment was operated in the positions ofupside down or turning sideways.

[0165] Thus, a compact fuel cell of 12 volt class could be attained bymounting multiple fuel cells on one outer wall surface of a liquid fuelcontainer, connecting in series with an interconnecter and connectingthe series cell groups mounted on multiple surfaces in parallel, withoutlaminating with a separator in between. In this case, a power sourcecould be obtained without requiring any auxiliary equipment such as afuel feed pump or a fan for cathode gas, by contacting an inner part ofthe container and an anode with a liquid fuel sucking material in ananode side and exposing a cathode to ambient air through a diffusionlayer.

[0166] This Example is characterized in that an output was improved byproviding a comparatively large power generation area, and it becomespossible to obtain a stable power generation in any position of thecontainer during operation. In addition, it also became possible inproduction of said power generation equipment, to easily fix each fuelcell using a heat shrinkable resin tube. EXAMPLE 5

[0167] A square type high output power generation equipment using aaqueous methanol solution as a fuel will be described. As an anodelayer, a porous membrane of about 20 μm thickness was formed by screenprinting of a slurry, which was prepared by mixing catalyst powder of50% by weight of fine particles of platinum/ruthenium alloy, in theatomic ratio of platinum/ruthenium being 1/1, dispersed and supported oncarbon carrier, 30% by weight of perfluorocarbone sulfonic acidelectrolyte (Nafion 117) as a binder and a water/alcohol mixed solvent(water:isopropanol:n-propanol is 20:40:40, ratio by weight).

[0168] As a cathode layer, a porous membrane of about 25 μm thick wasformed with a roll method using a slurry, which was prepared by mixingcatalyst powder of 50% by weight of fine particles of platinum supportedon carbon carrier and an aqueous dispersion of polytetrafluoroethyleneas a binder, so that the ratio by dry weight became 25% by weight. Thiscathode layer was fired in air at 290° C. for one hour to decompose asurfactant in the aqueous dispersion.

[0169] Thus prepared anode and cathode porous membranes were cut outeach in the size of 16 mm width×56 mm length to obtain an anode and acathode.

[0170] Then, Nafion 117 electrolyte membrane with the thickness of 50 μmwas cut out in the size of 120 mm width×180 mm length, and about 0.5 mlof a 5% by weight aqueous alcohol solution of Nafion 117 (from FlukaChemika Ltd.) was penetrated to anode layer surface, followed by joiningand drying at 80° C. for 3 hours under the load of about 1 kg. Then, asurface of cathode layer was penetrated with a 10% by weight aqueousalcohol solution of Nafion 117 (from Fluka Chemika Ltd.), so that thesolution became 25% by weight based on dry weight of the cathode,followed by joining so as to overlap with an anode layer joined inadvance, drying at 80° C. for 3 hours under the load of about 1 kg toprepare MEA.

[0171] A fuel container had the outer dimensions of 28 mm width×128 mmlength×24 mm height and was prepared by adhering rigid poly(vinylchloride) with the wall thickness of 2 mm using an adhesives. Similar toExample 2, 18 notches with the dimensions of 16 mm width×56 mmlength×0.1 mm depth were provided for fuel cell mounting in an outerwall of this hexahedron container.

[0172] Slits of 0.5 mm width×16 mm length were provided at the intervalof 0.5 mm in the central part of 16 mm width×56 mm length in a fuel cellmounting part. Eight air vent holes with a gas/liquid separationfunction and the inner diameter of 2 mm, the same as in FIG. 4A, wereprovided at four corners of two maximum surfaces of a fuel container.

[0173] An electroless nickel plated metalizing layer with the thicknessof about 50 μm was formed as an interconnector in an anode side in anotched part for fuel cell mounting in order to electrically connect inseries to an adjacent fuel cell in the same way as in Example 2. Slitsof 0.5 mm width×56 mm length were also provided at the interval of 0.5mm, in the part of a fuel cell mounting plate contacting to a cathode inmatching size with each outer wall surface of a fuel container in thesame way as in Example 2.

[0174] Further, a cathode current collector with a slit was mounted on afuel cell fixing plate. Output terminals connected in series were takenout from 18 fuel cells mounted on an outer wall surface of a fuelcontainer by a cathode current collector adjacent to an interconnectorin an anode side.

[0175] Thus obtained parts were laminated in the order of an anode sidegasket and MEA, and peripheral part of each fuel cell in a fuel cellmounting plate and peripheral part of a fuel container were joined withan adhesive. Thus obtained fuel cell power generation equipment was adirect current power generation equipment having the outer dimensions ofabout 28 mm width×128 mm length×28 mm height as shown in FIG. 19,mounted with 18 series of unit cells 13 with the power generation areaof about 9 cm² on a wall surface of a fuel container 1, and havingoutput terminals 16 and eight air vent holes 5 with a gas/liquidseparation function, at an upper and a bottom surfaces. A inside volumeof the fuel container was about 59 ml.

[0176] After filling about 55 ml of a 10% by weight of aqueous methanolsolution in the fuel container, a continuous power generation wascarried out at the load current of 1A, to give a stable voltage forabout 45 minutes at an output of 6.1 V.

[0177] With this fuel cell, no change in an output voltage, no leakageof the liquid fuel or no pressure rise in a fuel container was observedeven if the power generation equipment was operated in the positions ofupside down or turning sideways.

[0178] Thus, a compact fuel cell of 6 volt class could be attained bymounting multiple fuel cells on one outer wall surface of a liquid fuelcontainer, connecting in series with an interconnecter and connectingthe series cell groups mounted on multiple surfaces in parallel, withoutlaminating with a separator in between. In this case, a power sourcecould be obtained without requiring any auxiliary equipment such as afuel feed pump or a fan for cathode gas, by contacting an inner part ofthe container and an anode with a liquid fuel sucking material in ananode side and exposing a cathode to ambient air through a diffusionlayer.

[0179] This example enables a structure with a reduced number ofcomponent parts without lowering performance even if a diffusion layeris omitted, by giving a water repellency to a cathode catalyst layer bydispersing polytetrafluoroethylene to make a diffusion of water formedeasy.

[0180] The above description was made with reference to Examples,however, it is apparent to those skilled in the art that various changesand modifications may be done in the present invention within the spiritof the invention and the spirit and scope of the attached claims.

[0181] The present invention is characterized in that a container for aliquid fuel is used as a platform, fuel cells are mounted on its wallsurface, and said cells are electrically connected in series or in acombination of series and parallel.

[0182] Fuel cells are mounted on a fuel container as a platform andliquid fuel is sucked up and fed to each fuel cell by capillary force,by filling a liquid fuel holding material in said container.

[0183] Oxygen (an oxidizing agent) in air is fed through a diffusionhole in each fuel cell having power generation part in an outercircumferential surface. By this, a fuel cell having a simple systemwithout requiring auxiliary equipment for feeding fuel and an oxidizingagent can be realized.

[0184] By using an aqueous methanol solution having a high volume energydensity as a liquid fuel, a longer time of power generation per litterfuel can be attained compared with the case using hydrogen as a fuel,and a continuous power generation equipment without requiring chargingsuch as conventional secondary battery, can be obtained by sequentialfeeding of a fuel.

[0185] Furthermore, by mounting fuel cells on multiple wall surfaces ofa fuel container and providing multiple air vent holes having agas/liquid separation function on the wall surfaces, a power generationequipment providing stable and continuous power generation in anyposition of the fuel container can be attained.

1-9 (Canceled)
 10. A fuel cell power generation equipment in which ananode for oxidizing fuel and a cathode for reducing oxygen are formedwith an electrolyte membrane in between, and liquid is used as a fuel,wherein at least one opposing wall surface of a fuel container hasmultiple air vent holes each having a gas/liquid separation function, aliquid fuel holding material is filled on an inner wall surface of thefuel container, multiple unit cells consisting of an electrolytemembrane, an anode and a cathode having a diffusion layer are mounted onan electrically insulated outer wall surface of said fuel container, thediffusion layer is in contact with the liquid fuel holding material, andthe unit cells are electrically connected in series, parallel, or incombination of series and parallel each other. 11-13 (Canceled)